si2439-a-gm Silicon Laboratories, si2439-a-gm Datasheet - Page 45

• Manufacturer Part Number: si2439-a-gm
• Description: V.92 And V.34 Isomodem With Global Daa
• Manufacturer: Silicon Laboratories

Command
%V2
Table 12. Extended AT% Command Set (Command Defaults in Bold) (Continued)
Automatic Line Status Detection—Adaptive Method.
Description: Before going off-hook with the ATD, ATO, or ATA commands, the Si2494/39 compares
the line voltage (via LVCS) to the NLIU (U85) register:
Loop Voltage
0  LVCS  (0.0625 x NLIU)
(0.0625 x NLIU) < LVCS  (0.85 x NLIU)
(0.85 x NLIU) < LCVS
The NLIU register is updated every 1 ms with the minimum non-zero value of LVCS in the last
30 ms. This allows the Si2494/39 to eliminate errors due to 50/60 Hz interference and also adapt to
relatively slow change in the on-hook dc reference value on the telephone line. This algorithm does
not allow any non-zero values for NLIU below 0x0007. The host may also initialize NLIU prior to
issuing the %V2 command. Once the call has begun, the off-hook intrusion algorithm (described in
"4.16.2. Off-Hook Intrusion Detection" on page 23) operates normally. In addition, the Si2494/39 will
report “NO LINE” if the telephone line is completely disconnected. If the HOI (U77, bit 11) bit is set,
“LINE IN USE” is reported upon intrusion.
Rev. 1.0
Action
Report “NO LINE” and remain on-hook.
Report “LINE IN USE” and remain on-hook.
Go off-hook and establish a modem connection.
Action
Si2494/39
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